Recently I Notices Clusters, The Size Of A Nickel, Of

Recently I notices clusters, the size of a nickel, of black specks (smaller than blackheads and not raised) on different parts of my body. Both forearms and now 2 spots on my shoulder and 1 on my hip. I can "pop" them to remove the black speck but I'm wondering what this is, I have a hard time believing it's just dirt when it's a series of clusters. I'm a 22 year old male in good shape in Seattle and haven't visited anywhere recently.